1. Field of the Invention
This invention relates to an ink jet printer recording head which records an image on a recording medium by ejecting ink droplets.
2. Prior Art
Disclosed in Japanese Patent Examined Publication No. 8957/1985 is an on-demand type ink jet printer, in which piezoelectric conversion members are formed behind and slightly spaced apart from a substrate having nozzles thereby leaving a small gap between each piezoelectric conversion member and the substrate. A voltage is applied to the piezoelectric conversion members to cause them to be displaced thereby pressuring ink present between the piezoelectric conversion members and the substrate to attendantly eject the pressured ink through the nozzles in the form of ink droplets.
Compared to a general ink jet printer in which the ink is ejected by changing the volume of the ink chamber using the piezoelectric conversion members and by guiding the ink within the ink chamber to nozzles, the ink jet printer described above has each piezoelectric conversion member positioned adjacent to each nozzle and is displaced in the axial direction of the nozzle, so that it not only shortens the flow path of the ink and enhances the ink ejection efficiency and stability but is advantageous in that the piezoelectric conversion member can be operated without such disturbances as infiltration of air bubbles or dust in the ink.
In such an ink jet printer it is the gap between each piezoelectric conversion member and the substrate that plays an important role in determining the ejection speed and amount of discharged ink droplets, or the ejection response. In general, each piezoelectric conversion member, with its construction involving a laminate formed of a piezoelectric element and a metal plate, is subject to warp due to differences in thermal expansion coefficients of these two materials, thereby making it impossible to maintain a constant distance between the piezoelectric conversion member and the substrate. As a result, there exists not only the problem that the level of density fluctuates depending on the temperature, but also the extreme difficulty of making the piezoelectric conversion member thin thus losing the advantage of reducing the required drive voltage.